The format of the Boot command is now as follows:–
| B | Boot drive A, double density, sector 0, 5.25 inch |
| or |
| B sscd | Where sscd is a single hexadecimal value. |
| Leading zeroes may be omitted. |
| ss | is the physical sector number to be read. Normally this is 0 or 1. |
| c | is the command digit which has the following possible values:– |
| 0 | 5.25 inch, double density |
| 1 | 5.25 inch, single density |
| 3 | 8 inch, single density |
| d | is the drive select digit which has the following possible values:– |
| 1 | drive A |
| 2 | drive B |
| 4 | drive C |
| 8 | drive D |
Examples of the enhanced Boot command
| B 2 | Sec 0, 5.25 inch, DD, drive B |
| B 111 | Sec 1, 5.25 inch, SD, drive A |
| B 134 | Sec 1, 8 inch, SD, drive C |
Patches Required
First make the patches to bring V2.0 to V2.1, if needed.
| Address | V2.0 | V2.1 |
|---|
| F068 | 30 | 31 |
| F108 | 20 | ED |
| F109 | 04 | A1 |
| FI0A | ED | 20 |
| F10B | 41 | 02 |
Then make the patches to bring V2.1 to V2.3.
| At F068 change | 31 to 33 |
| At FB08 change | 3A 60 00 to CD EF FF |
| At FC03 change | 11 99 FC to 3D 20 FD |
| At FC11 change | 20 27 3E D0 CD 8C FC 3E 01 D3 E4 36 5B |
| to | 11 99 FC 20 24 3E D0 CD 8C FC CD DE FF |
| At FC42 change | AF D3 E2 to 00 00 00 |
| At FFDE there are FF characters to the end – change these to |
| 3A 61 00 B7 20 01 3C D3 |
| E4 3A 62 00 D3 E2 3E 5B |
| C9 3A 60 00 B7 20 06 21 |
| 00 00 22 61 00 FE 02 D0 |
| AF C9 |
These changes have been carefully checked and the results fully tested,
so you should have no difficulty. You can check that you have typed in the
changes correctly by using the standard CRC calculating program. For your
convenience this program has been run separately on the first 2K of RP/M V2.3
(CRC = EF 24) and the second half (CRC = 58 CD). Therefore you can easily
confirm that your new RP/M 2.3 is correct. The CRC calculating program is
called CRC.COM and is the subject of
another article in this issue.